25 June 2026, Volume 37 Issue 2

    

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DIGITAL INTELLIGENCE APPLICATION
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  Construction and application of offshore oilfield mud logging intelligent knowledge system based on improved Retrieval-Augmented Generation （RAG） technology

  WANG Hongna, HOU Qunqun, FANG Zhendong, JIANG Hui, SHEN Wenjian

  Mud Logging Engineering. 2026, 37(2): 1-8. https://doi.org/10.3969/j.issn.1672-9803.2026.02.001

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  To address the challenges in offshore oilfield mud logging operations,including diverse data types professional knowledge crossover,response lag,and complex network conditional complexity,an improved Retrieval-Augmented Generation （RAG） intelligent knowledge system-OffshoreRAG has been proposed and implemented. Based on the traditional RAG framework,the system introduces domain-oriented enhancements：for the first time,professional data such as mud logging curves are deeply integrated through a multimodal knowledge processing supported by a metadata-based knowledg management structure. A hybrid retrieval strategy adopting structural tags with vector recall is designed,incorporating a Cross-Encoder for fine-grained semantic re-ranking. And in PostgreSQL,pgvector columns,table partitioning,and parallel execution plans are integrated to achieve second-level response mechanism,forming a traceable closed-loop process from data acquisition to question and answer generation. Experiments using over 1 800 real offshore oilfield mud logging reports,well test design files,and equipment documents as multimodal data constructed a test set of 1 000 queries covering operational procedures,equipment fault diagnosis,and standards lookup. Field deployment application results show that the system effectively integrates multi-source information,significantly enhancing engineers' decision-making efficiency and emergency response capability in high-intensity work environments. The results demonstrate the feasibility and significant advantages of multimodal RAG systems tailored to specific industrial scenarios. In the future by expanding real-time curve data access capability,increasing concurrency and latency simulation tests,and optimizing curve feature extraction and storage strategies,the system's stability and engineering value under complex offshore conditions is further improved.
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  Construction of an intelligent digital production management system for unattended gas gathering stations in gas fields

  BAI Haofeng, XU Jice, CHEN Tianying, LI Hongxi, LIU Mengpeng, HUANG Hanjun

  Mud Logging Engineering. 2026, 37(2): 9-18. https://doi.org/10.3969/j.issn.1672-9803.2026.02.002

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  To ensure efficient and safe operation of gas gathering stations in oil and gas fields ,based on analyzing the existing production process,equipment management and safety guarantee system of gas gathering stations,the paper takes the production management of gas gathering stations in Sulige Gas Field as an example to points out the efficiency limitations of the traditional mode under complex working conditions and large-scale production. A full-link integrated intelligent digital management and control system of "sensing-transmission-governance-decision-execution" is constructed to realize efficient collaboration and intelligent control of the whole production process. The system mainly has three core modules：digital infrastructure,data fusion platform and intelligent analysis application. Field application shows that compared with manual operation,the intelligent digital system shows faster response,higher regulation accuracy,better production control efficiency,smaller production fluctuation and more stable natural gas supply. The digital-intelligent construction of production management for unattended gas gathering stations is of great significance in optimizing production management,strengthening safety guarantee,improving production efficiency,reducing operation cost and realizing resource optimization.
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  Construction and application of drilling equipment integrity management system

  WANG Hubin

  Mud Logging Engineering. 2026, 37(2): 19-26. https://doi.org/10.3969/j.issn.1672-9803.2026.02.003

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  Aimed at issues in drilling site equipment management,such as dispersed ledgers,disperse offline processes,inconsistent data standards,and difficulty in management traceability,a drilling equipment integrity management system has been constructed. Based on a Vue+Java technology,the system adopts a front-end/back-end separation architecture,building a three-layer technical structure consisting of a perception layer,platform layer,and application layer. The four-level organizational structure encompasses six core functional modules. The system is based on unified data,establishing a data system including equipment classification and grading,equipment ledgers,and technical archives： At the business level,it implements online closed-loop key processes such as operation records,maintenance management,inspections and testing,and allocation and archiving： At the management level,it provides capabilities for electric （gas） replacing oil management,quarterly and annual reporting management,and visual analysis,while ensuring multi-level standardized use through role permissions and user management. Application results from Liaohe,Changqing,and Sichuan areas indicate that the system supports PC and mobile collaboration,with a comprehensive dashboard enhancing rapid identification of asset structure and risk status. The task-based workflow mechanism on the mobile application effectively improves overall execution in field operation and maintenance,evidence retention,and closed-loop tracking,promoting the transition of equipment management from offline and dispersed to online and collaborative,providing platform support and decision-making basis for full lifecycle integrity management of drilling equipment.
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  Intelligent lithology homing method based on deep learning：Taking well ZJ 143 in Zhongjia Block as an example

  LOU Lin, PENG Jieshi, LI Zhe, LI Ruizhu, ZHANG Bo, WANG Duo

  Mud Logging Engineering. 2026, 37(2): 27-33. https://doi.org/10.3969/j.issn.1672-9803.2026.02.004

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  During oil and gas exploration and development,accurate identification of formation lithology serves as the fundamental work for reservoir evaluation,hydrocarbon-bearing zone identification,and drilling operation guidance. Traditional lithology identification methods suffer from high cost,long cycle time,and poor spatial continuity,making it difficult to meet the demands of modern high-efficiency exploration. Therefore,it is urgent to develop an efficient and automated lithology identification method using geophysical data. To this end,this study integrates the U-Net network with a residual network to perform lithology homing using well logging data,aiming to reduce manual workload and improve identification accuracy and efficiency through deep learning models. The residual blocks introduced into the model to enhance the efficiency and stability of feature extraction,while the attention module improved sensitivity to lithological boundaries. Moreover,compared with traditional processing workflows,the well logging curves are standardized during the data preprocessing stage,and a depth-slice dataset is constructed via statistical median extraction to enhance the model's generalization ability and interpretability. The research results indicate that,compared with traditional manual lithology homing,the deep learning-based method offers advantages such as higher classification accuracy and more precise homing identification. The method was applied to well ZJ 143 in the Zhongjia Block,achieving an identification accuracy of 93.8% and a speed increase of 6-8 times compared to manual interpretation.
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  Mud logging interpretation chart intelligent generation and intelligent interpretation technology

  GUO Yafei, TIAN Weizhi, SONG Minghui, DU Peng, WANG Yu, XU Zhe

  Mud Logging Engineering. 2026, 37(2): 34-42. https://doi.org/10.3969/j.issn.1672-9803.2026.02.005

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  To address the issues of traditional mud logging interpretation charts relying on manual drawing,inconsistent standards,low efficiency,strong subjectivity,and difficulty in meeting the demands of fine mud logging interpretation for complex hydorcarbon reservoirs,intelligent generation and intelligent interpretation technology for mud logging interpretation charts were researched and developed.It uses adjacent well mud logging data as the core data source,collecting key mud logging parameters such as gas logging,rock pyrolysis,and light hydrocarbons,and completing data cleaning and standardization preprocessing. Use the grey relational analysis method to screen sensitivity parameters that are highly correlated with reservoir oil-gas bearing properties,and build an intelligent chart generation model. By combining with a Bayesian-weighted global-local fusion method,the boundary lines of the intersection charts are scientifically delineated,simultaneously generating standardized mud logging interpretation charts and quantitative interpretation standards adapted to the study area. Construct a comprehensive scoring evaluation model of multiple indicators based on the entropy weight method.Compare and analyze the target well mud logging data with the generated charts and standards,and automatically output mud logging interpretation conclusion of the target horizons through the intelligent discrimination algorithm. Select data from multiple adjacent wells in block G of Liaohe Oilfield for experimental verification. After this technology was applied to the interpretation of target horizons,the accuracy rate of small-layer discrimination in the block reached 94.64%,the interpretation coincidence rate was increased by 5.78% compared with traditional manual interpretation,and the efficiency of single-well interpretation was improved by more than 97%. This enhanced the accuracy,consistency and efficiency of mud logging interpretation. The practice has shown that this technology can achieve efficient reuse of adjacent well data and automated generation of interpretation charts and standards,effectively improve the intelligence level and interpretation accuracy of mud logging interpretation,adapt to complex hydrocarbon reservoir mud logging interpretation scenarios,and possess good engineering practicality and promotion value.
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  R&D and application of a large model for lost circulation and drill pipe sticking risk scenarios

  SONG Jiaxing

  Mud Logging Engineering. 2026, 37(2): 43-49. https://doi.org/10.3969/j.issn.1672-9803.2026.02.006

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  The current artificial intelligence early warning technology for drilling safety can only process single-modal data,be difficult to integrate multi-source information,and lack a cross-validation mechanism,making it difficult to build a complete chain of explanation and analysis. To address the technical issues in the intelligent construction of oil and gas wellbore engineering risk areas,such as edge data cleaning,multimodal model research and development,and model collaborative reasoning,and to comprehensively enhance the level of drilling risk warning,a large model for lost circulation and drill pipe sticking risk scenarios has been successfully developed and applied by adopting the methods of lost circulation and drill pipe sticking events automatic identification for multi-model collaborative reasoning,ultimately achieving the monitoring of over 12 drilling risk related parameters at the second level. Applications in the Liaohe and Southwest oil & gas fields indicate that,compared with the traditional single risk models,this model improve risk identification rates for lost circulation and drill pipe sticking to 88.89% and 89.23% respectively,the daily false alarm times are controlled below 10,and daily real-time data analysis and automatic abnormal report generation for 50 wells are achieved. The practical implementation of this model services verified the effectiveness of the large model for lost circulation and drill pipe sticking risk scenarios in the oil and gas wellbore engineering field. The model provides technical support for the intelligent development of regional companies.
EQUIPMENT R & D
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  Development and application of remote automatic calibration system for chromatograph

  ZENG Hongen, CUI Bo, XIE Jun, PENG Jun, QI Lin, SUN Guanghui

  Mud Logging Engineering. 2026, 37(2): 50-56. https://doi.org/10.3969/j.issn.1672-9803.2026.02.007

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  Chromatograph is the core testing equipment of gas logging data analysis in geological logging industry. It is necessary to calibrate the chromatograph when the new well is put on at the beginning,stopped for a long time and started after maintenance. However,the traditional manual calibration method has some problems such as too long calibration time,complicated operation and difficult to control the accuracy. Therefore,the remote automatic calibration system of chromatograph is developed in this paper. Through modularization and integrated circuit design,it is equipped with a highly integrated automatic calibration chassis,which is pre-connected to standard gas cylinders with different concentrations. During the calibration process,it automatically completes the operations of gas circuit switching with different concentrations,standard sample gas collection and analysis,data storage and writing,etc. Finally,it can complete the calibration of each concentration of the chromatograph within 12 min,forming a calibration template,and realizing the remote control,one-click and fully automatic calibration of the whole process. The calibration system has low technical threshold,can be maintenance-free for a long time,realizes remote,automated and intelligent operation,and adapts to the new mode of "remote logging and intelligent mud logging" in the logging industry.
TECHNOLOGY
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  Analysis on the collapse of crushed coal seam borehole with spalling detachment as the control condition

  DAI Guangkuo, XU Tiecheng, WANG Xiaojiang, LIU Yue, HU Lin, WANG Leyu

  Mud Logging Engineering. 2026, 37(2): 57-65. https://doi.org/10.3969/j.issn.1672-9803.2026.02.008

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  To predict the borehole collapse behavior during drilling in crushed coal seams,the equilibrium theory and Hoek-Brown criterion were introduced. With the shear occurring and tensile failure in cleats as the critical conditions for spalling detachment,the sliding criteria for quadrilateral spalling and triangular spalling were established. The accuracy of the proposed criteria was verified by using the PFC（Particle Flow Code） software to compare the detachment results of the spalling under the same conditions. The results obtained by applying the proposed criteria to discuss the impact of cleat geometry parameters （spacing,length,angle） and the geometric position of the spalling on borehole collapse show that,under the same area,quadrilateral spalling is more prone to detachment than triangular spalling. Larger spacing of face cleats and larger inclination angle of cleats are beneficial for maintaining the stability of quadrilaterals,but dangerous for triangles. A larger end cleat spacing is not conducive to the stability of quadrilateral spalling,but beneficial for the stability of triangular spalling. Larger face cleat length is beneficial for the stability of quadrilateral spalling and triangular spalling. As the spalling geometric position changes,the shear sliding coefficient and equilibrium sliding coefficient of the quadrilateral spalling vary sinusoidally,while the equilibrium sliding coefficient of the triangular spalling also exhibits a sinusoidal variation. However,the shear sliding coefficient shows wave-like variations without any distinct symmetry law.This study has important engineering significance for improving the analysis of borehole collapse during coalbed methane drilling.
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  Application of geology-engineering integration fast and slow loop iterative technology system to the reserves that are hard to put into production

  LI Chen, XU Shengchi, HU Xiaoling, LI Sheng, LI Honglin, MA Jun

  Mud Logging Engineering. 2026, 37(2): 66-76. https://doi.org/10.3969/j.issn.1672-9803.2026.02.009

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  In response to the challenges faced in the reserves that are hard to put into production in China,such as strong reservoir heterogeneity and complex engineering conditions,a "intelligent+diversified" 3D geological modeling and dynamic technology system has been constructed based on the fast and slow loop iterative theory of geology-engineering integration. This system achieves the collaborative optimization of geological understanding and engineering execution through the real-time data mutual feedback and dynamic iteration between the slow loop （geological modeling and conceptual design） and the fast loop （drilling construction and fracturing implementation）.Key technologies include holographic spread-spectrum fracture identification technology based on deep learning,"rotary steering+screw" composite drilling speed-up template and "dense cutting+CO₂ energy storage" differentiated fracturing process. In the application of block D 13 in Xinjiang Oilfield,the drilling cycle has been shortened from 133 d to 60 d,with a complex time efficiency of less than 1.8%. The estimated ultimate recovery （EUR） of a single well has reached 4.3 × 10⁴ t,achieving economic development of reserves that were hard to put into production. This achievement provides theoretical methods and technical models for the intelligent development of unconventional oil & gas reservoirs,and it has guiding significance for ensuring national energy security.
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  Differentiated horizon determination method for drilling coring in shallow lithologic reservoirs based on reservoir classification

  MA Fugang, LI Zhankui, HUA Caihong, LIU Chunxi, MA Huaiyu, XIE Yingming

  Mud Logging Engineering. 2026, 37(2): 77-84. https://doi.org/10.3969/j.issn.1672-9803.2026.02.010

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  The shallow lithologic reservoirs of the Minghuazhen Formation in the Neogene system of the Bohai Bay is currently a key area for increasing reserves and production. For reservoirs with typical characteristics such as rapid lateral changes,thin single-layer thickness,frequent interbedding of sandstone and mudstone,and internal interlayer development,they bring challenges to precise horizon determination for drilling coring. The traditional methods are prone to problems such as thin layer penetration,interlayer clogging,and low recovery of high-quality reservoirs in thick layers,a differentiated coring and horizon determination method based on seismic profile 90° phase shift technology is proposed. This method is based on reservoir classification. By constructing pre-drilling identification graphs for three types of reservoirs,i. e.,thick massive reservoirs,thick reservoirs with interlayers,and thin reservoirs,it forms a differentiated horizon determination operation plan of "one type,one strategy". The practical application in 8 wells of Bohai Oilfield has shown that this method has achieved a shift in the operation mode of coring and horizon determination from "passive following" to "active navigation". The accuracy of the horizon determination reaches 100%,and the rate of drilling the reservoir reaches 98.32%,effectively improving the accuracy of obtaining high-quality reservoir cores. It also provides new operational ideas for precise coring and efficient exploration of Bohai Oilfield and similar shallow complex lithologic reservoirs.
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  Overflow law and geological main controlling factors of shale gas Silurian strata in Luzhou

  XIAO Wentong

  Mud Logging Engineering. 2026, 37(2): 85-92. https://doi.org/10.3969/j.issn.1672-9803.2026.02.011

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  The Silurian deep shale gas resources are abundant in Luzhou Block,Sichuan Basin. However,due to the superposition of multi-stage tectonic movements,overflow accidents occur frequently during drilling,which seriously restricts the effective development of the block. The overflow data of 33 wells in 24 development wells in Luzhou block from 2022 to 2024 are systematically sorted out. From the three dimensions of loss time,occurrence horizon and genetic classification,the vertical and horizontal distribution law of overflow in Silurian strata is revealed. It is clear that abnormal high pressure,low actual drilling density and drilling faults are the main causes,accounting for 53%,18% and 15% respectively. On this basis,coupled with the sedimentary evolution and fault development characteristics of Silurian,the control effect of "three elements" of gas source supply,migration channel and reservoir space on overflow is analyzed,and three types of overflow geological models of "fault dredging type" "dessert enrichment type" and "reservoir heterogeneity type" are proposed and constructed. The identification marks,drilling performance and disposal difficulty are compared and analyzed,in order to provide geological basis and theoretical guidance for the prevention and control of well control risk of similar deep shale gas drilling in the future.
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  Study and application of efficient development horizon optimization method for low-resistivity oil layers：Taking Yangerzhuang Oilfield as an example

  WU Xiaona

  Mud Logging Engineering. 2026, 37(2): 93-97. https://doi.org/10.3969/j.issn.1672-9803.2026.02.012

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  Tapping the potential of low-resistivity oil layers is crucial in reservoir development. Because the resistivity of low-resistivity oil layers is similar to that of water layers,traditional well logging interpretation conclusions can easily mislead development technical personnel's judgments,causing its potential to be overlooked. Therefore,an in-depth study and summary of the oil well measures implemented in Yangerzhuang Oilfield over the past 15 years were conducted. By re-conducting well logging and mud logging evaluations and combining them with reservoir production law,the new evaluation criteria for low-resistivity oil layers have been established. On this basis,by fusion of static parameters （resistivity,mud logging shows,effective thickness,interval transit time） and dynamic parameters （recovery percent of recoverable reserves）,a comprehensive factor of λ and a horizon optimization chart were constructed,determining that λ greater than or equal to 117 is the threshold for efficient development measures. The practical application shows that in Yangerzhuang Oilfield,14 wells implemented the measure of increasing the perforated intervals. In the initial stage,the daily oil production increased by 116.8 t,and the cumulative oil production increased by 7 895 t. The success rate of measures has increased to over 85%,effectively tapping into the potential of low-resistivity oil layers and achieving increased production and efficiency. This technology not only significantly improves the accuracy and efficiency of identifying low-resistivity oil layers,but also provides key technical support for the optimization of measures for developing oil wells with low-resistivity oil layers,which has important practical significance for improving the development effects of similar reservoirs.
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  Application of element logging in blind side-tracking of deep carbonate formation：A case study of well PX 101 in Penglai Gas Field,Sichuan Basin

  LIU Hengyu, GAO Ping, DING Wei, MO Qianwen, YANG Cong, HUANG Kun

  Mud Logging Engineering. 2026, 37(2): 98-106. https://doi.org/10.3969/j.issn.1672-9803.2026.02.013

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  In order to solve the problem that it is difficult to quantitatively control the wellbore trajectory in blind side-tracking of PX 101 deep ultra-high pressure complex well in carbonate formation in Penglai Gas Field,Sichuan Basin,this paper analyzes the element composition and identification elements of rock cuttings and cement plugs based on high-precision element analysis technology,establishes a multi-linear regression identification model,and realizes the trajectory control of blind side-tracking of deep ultra-high pressure complex well. The results show that：（1）The characteristic identification elements of formation cuttings and cement plugs are Mg,Si,Al,Ca,Fe;（2）Based on the characteristic identification elements,multi-linear regression is established to calculate the side-tracking coefficient. According to the side-tracking coefficient while drilling,multi-factor comprehensive quantitative control of the wellbore trajectory change can be realized. The multiple linear regression model established by element logging technique can quantitatively evaluate the proportion of cuttings,wellbore trajectory change and wellbore stability of blind side-tracking. This study has achieved good application effect in blind side-tracking of PX 101 deep ultra-high pressure complex well.
INTERPRETATION & EVALUATION
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  Main controlling factor analysis and prediction methods for gas concentration in deep coal-rock gas reservoirs

  ZHANG Wenya, SHI Yanfei, WANG Xijun, WANG Candanting, YANG Zuhe

  Mud Logging Engineering. 2026, 37(2): 107-114. https://doi.org/10.3969/j.issn.1672-9803.2026.02.014

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  The accurate assessment of the gas concentration in deep coal-rock gas reservoirs is crucial for the prediction of resource potential and the selection of development sweet spots. In response to the bottleneck of high cost and poor timeliness in traditional coring desorption methods,this paper systematically analyzed the occurrence mechanism of deep coal-rock gas using the No.8 coal in the Ordos Basin as the research object,and clarified seven main geofactors,including macro coal-rock type,coal-rock reservoir thickness,coal content,ash content,metamorphic grade,total organic carbon content （TOC）,and sealing gland thickness. On this basis,the while drilling data from gas logging,geochemistry,and element logging etc.,were used to screen sensitive parameters. A gas concentration comprehensive prediction model was established through the multi-parameter fusion method. The model applied in Block X of the Ordos Basin achieved a prediction accuracy of over 85%. By combining the reservoir hydro-fracturing potential characterization parameters,the geology-engineering dual sweet spot comprehensive evaluation standards were formed,significantly improving the efficiency of sweet spot identification and the timeliness of exploration decisions,providing new theoretical basis and technical means for the economically efficient development of deep coal-rock gas.
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  Exploration of the application of DRIFTS cuttings logging technology to dual-deep overpressure well： A case study of Wenchang A Sag,the Pearl River Mouth Basin

  LIU Shibin, HU Yitao, NI Pengbo, LIU Hongkun, ZHONG Peng, WEI Xiaoxin

  Mud Logging Engineering. 2026, 37(2): 115-123. https://doi.org/10.3969/j.issn.1672-9803.2026.02.015

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  In the absence of LWD data,in order to ensure the timely and accurate lithology identification,reservoir physical property evaluation,pressure monitoring while drilling for deep high pressure formation in Wenchang A sag,the Pearl River Mouth Basin,as well as to meet the needs of multi-technology fusion,DRIFTS（Diffuse Reflectance Infrared Fourier Transform Spectroscopy） cuttings logging technology was introduced.Taking the application of well WC-X 1 in Wenchang A Sag of the Pearl River Mouth Basin as an example,based on the analysis of the technical principles,the sample analysis and processing workflow was optimized,and a study on multiple linear regression fitting of natural gamma （D_GR） based on mineralogical analysis was carried out. Based on TOC and maturity parameters,the source rocks are evaluated. Comprehensively evaluate the pressure while drilling based on montmorillonite content,TOC,and other parameters. Evaluate reservoir quality through the mineral reservoir quality index （D_RQI）,and establish reservoir classification standards based on logging porosity and the mineral reservoir quality index. This standards are used for rapid evaluation and decision-making while drilling,showing the excellent prospects of this technology in the field of interpretation and evaluation while drilling.
GEOLOGICAL RESEARCH
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  The coupling characteristics of microscopic-macroscopic heterogeneity in the Yan 9 reservoir of Jingbian Oilfield,Ordos Basin

  LI Gang, ZHANG Jinfeng, DANG Xiaofeng, LU Haoguo, YIN Dianzheng, ZHANG Zhiquan

  Mud Logging Engineering. 2026, 37(2): 124-131. https://doi.org/10.3969/j.issn.1672-9803.2026.02.016

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  Aiming at the technical problems of uneven water injection effect and low injection-production correspondence rate caused by unclear understanding of the heterogeneity of Yan 9 reservoir in Jingbian Oilfield of Ordos Basin,comprehensive core analysis,well logging interpretation and quantitative statistics were used to study the heterogeneity from the perspectives of pore type and structure,reservoir particles and vertical grain size,interlayer and plane pore saturation （porosity,permeability and oil saturation）. Through the multi-dimensional heterogeneity correlation analysis of "pore-throat-particle-interlayer-plane-quantitative evaluation",a quantitative coupling evaluation system of reservoir micro-macro heterogeneity was constructed. The results show that the Yan 9 reservoir has a positive rhythm,the sorting coefficient is 7.75,the variation coefficient of porosity and permeability ratio is between 0.72 and 0.89,the interlayer thickness is 2.1-4.5 m,the difference of porosity,permeability and oil saturation plane is significant,and the Lorenz curve-Gini coefficient is between 0.24 and 0.31. The comprehensive evaluation shows that the Yan 9 reservoir is characterized by strong heterogeneity as a whole,and the heterogeneity of Yan 9₂² layer is the most prominent. The research results can provide geological basis and technical reference for well pattern optimization,water injection dynamic adjustment,remaining oil potential tapping and efficient development of tight sandstone reservoirs of the same type in this area.
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  Geochemical characteristics and hydrocarbon generation potential prediction for the source rocks from the third Member of the Dongying Formation in the deep subsag area of Qikou Sag

  XU Wenjing, ZOU Leiluo, LIU Guoquan, CUI Yu, CHEN Jiaxu, WANG Guan

  Mud Logging Engineering. 2026, 37(2): 132-140. https://doi.org/10.3969/j.issn.1672-9803.2026.02.017

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  The exploration level in the deep subsag area of Qikou Sag is low. The study on the hydrocarbon generation potential of the source rocks from the third Member of Dongying Formation and the understanding of the oil and gas resource potential are weak,which have become important factors restricting the oil and gas exploration in this area. Therefore,by comprehensively applying analysis assay data of total organic carbon content（TOC）,kerogen macerals,vitrinite reflectance（R_o） and biomarkers,from well H 1,and the multiple peripheral wells such as T 20X1 in the deep subsag area of Qikou Sag,and the study on the geochemical behavior and hydrocarbon generation potential of the source rocks from the third Member of Dongying Formation in the deep subsag area of Qikou Sag,the three-dimensional spatial distribution of favorable source rocks was described and the hydrocarbon generation potential of the source rocks in the study area was clarified. The results indicate that the source rocks from the third Member of Dongying Formation in the deep subsag area of Qikou Sag have an average TOC of 3.51% and an average R_o of 1.26. The organic matter types are mainly Ⅱ₁-Ⅱ₂,and the overall performance of the source rocks is good-high quality level,and they are in the mature evolutionary stage. The sedimentary environment is generally weak oxidation-weak reduction,with low salinity environment,and is dominated by mixed sources and inputs from phytoplankton. The high quality source rocks from the third Member of Dongying Formation in Qikou Sag are mainly distributed in the middle and lower submembers of the third Member of Dongying Formation. The source rock are distributed in a widespread covering pattern. The zones of thick source rocks are mainly concentrated in the deep subsag area. The thickness of source rocks form the third Member of Dongying Formation in the deep subsag area is 280-320 m,with an effective source rock area of 135 km² and a calculated resource of about 1.46×10⁸ t. Therefore,the source rocks from the third Member of Dongying Formation in the deep subsag area of Qikou Sag have great potential for hydrocarbon generation and are conducive to the development of self-generating and self-preserving hydrocarbon reservoirs. Further exploration and development efforts should be increased to find the advantageous production areas.
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  Sand control mechanism and accumulation characteristics of Es₃ in Qibei slope

  LI Xiaojing, ZHOU Jing, LI Weilong, ZHAO Jun, ZHOU Kejia, JI Jianzheng

  Mud Logging Engineering. 2026, 37(2): 141-151. https://doi.org/10.3969/j.issn.1672-9803.2026.02.018

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  The Qibei slope in the Qikou Sag is adjacent to the hydrocarbon generation center of the main Qikou Depression,possessing significant resource potential. However,strong lateral variations in reservoir distribution and complex hydrocarbon accumulation processes have restricted the progress of detailed exploration. Through analysis of segmented differential activity of syndepositional faults combined with variations in stratal thickness,this study reveals that small-scale antithetic syndepositional faults in the high slope segment complicate the paleogeomorphology,causing sand bodies to advance along main troughs toward paleo-high areas and extend laterally along secondary troughs. Oil-source correlation,fluid inclusion analysis,and accumulation studies indicate that the Qibei slope experienced two stages of hydrocarbon charging. The first stage of hydrocarbon migration occurred during the depositional period of the Dongying Formation,with hydrocarbons migrating to the middle slope,where a "dual unconformity+vertical fault" oil supply system predominated. The second stage of hydrocarbon migration occurred from the early depositional period of the Minghuazhen Formation to the present,with hydrocarbons migrating to the middle and high slope. During this stage,a "triple unconformity+vertical fault" oil supply system developed in the middle slope,while a "dual unconformity+vertical fault" oil supply system developed in the high slope. The study results identify favorable sand body enrichment zones in the study area,clarifies the hydrocarbon migration processes and favorable exploration targets,provides guidance for exploration deployment on the Qibei slope,and offers a reference for sand body prediction and hydrocarbon potential assessment in similar types of faulted basins.
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  Identification and description of buried denudation traps in the second Member of Shahejie Formation in Caoqiao north area,Dongying Sag

  DING Baojun

  Mud Logging Engineering. 2026, 37(2): 152-158. https://doi.org/10.3969/j.issn.1672-9803.2026.02.019

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  The Chaqiao North area in Dongying sag,Jiyang Depression has developed multi-layered and multi-type stratigraphic trap reservoir. However,due to the low precision and poor accuracy of the overburden and erosion line delineation,the exploration of such oil reservoirs is highly risky. Therefore,this paper proposes a method for effectively identifying and describing concealed erosion traps under geological condition constraints by using geophysical techniques. Specifically,the unconformity interface identification technology based on comprehensive logging curves is utilized to achieve fine comparison of the residual strata in the overburden and erosion zone. The instantaneous phase attribute and angle extrapolation technology are employed to accurately determine the location of the erosion point. By combining frequency division and well-point sand thickness statistics as the basis,the sand body distribution is determined under multi-well constraints. Through the three-line delineation,the matching relationship between the stratum line,reservoir line,and cap rock line is confirmed,and on this basis,the oil layer is delineated and the reserves are calculated. The technology proposed in this paper has been successfully applied to the Sha 2 section in the Caoqiao North area,achieving good exploration results. The favorable oil-bearing area of the remaining stratum traps in the Sha 2 section is determined to be 5.33 km²,and the predicted geological reserves of petroleum are 5.46 million tons. The technical achievements have reference significance for the identification of similar stratigraphic traps and the precise determination of erosion lines in other areas.